1. Field of the Invention
The present invention relates to an organic electroluminescent (EL) device, and more particularly, to an organic EL device including a blue light emitting layer which contacts red and green light emitting layers.
2. Description of the Related Art
Organic EL devices typically comprise a plurality of layers, such as a first electrode, a second electrode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, etc. Organic EL devices may be produced using a polymer material or a small molecule material. In a small molecule organic EL device, layers are formed by vacuum deposition. In a polymer organic EL device, light emitting elements are formed by spin coating.
The small molecule organic EL device may be obtained by forming an organic multi-layer including, for example, a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, an electron injection layer, etc. on a substrate using deposition, and forming a cathode on the organic multi-layer.
When manufacturing such a small molecule organic EL device, a hole injection layer and a hole transport layer are deposited, and then, R, G, and B regions electrically connected to the hole injection layer and the hole transport layer are each deposited using a shadow mask and patterned. Next, a hole blocking layer and an electron injection layer electrically contacting the R, G, and B regions are sequentially deposited on the resultant structure, and then, a cathode is deposited on the electron injection layer.
In the small molecule organic EL device, a fluorescent element or a phosphorescent element can be obtained by forming layers using vacuum deposition. However, when producing a full-color element, the layers are deposited using a mask, which prevents efficient mass production (see U.S. Pat. Nos. 6,310,360, 6,303,238, and 6,097,147).
In a polymer organic EL device, when red, green, and blue polymer layers are patterned using inkjetting or laser induced thermal imaging (LITI), light emitting efficiency, and lifetime may be decreased.
Thus, to manufacture organic EL devices according to a conventional method, R, G, and B must be separately micro-patterned, which is a limit to the efficiency of processes in all the methods of manufacturing organic EL devices.
When a red region (R), a green region (G), and a blue region (B) are formed in a pixel region according to a conventional method of manufacturing organic EL devices, pattering must be performed at least three times through deposition or transferring and the R, G, and B must be micro-patterned, and thus, misalignment may occur. Further, since holes moves faster than electrons in the pixel region, the hole blocking layer must be formed on the light emitting layer to prevent hole transfer. That is, a further process of forming the hole blocking layer is required.